PROTEIN FUNCTIONALITY IN FOOD
SYSTEMS EXAM QUESTIONS WITH CORRECT
ANSWERS
5 major functional properties of proteins - Correct Answers -1. Solubility
2. Water-holding ability
3. Gelation
4. Emulsification
5. Foaming
Give an example of a food system where the protein functional property of gelation is
important - Correct Answers -muscle foods, eggs, yogurt, gelatin, tofu, baked goods
Give an example of a food system where the protein functional property of water holding
ability is important - Correct Answers -muscle foods, cheese, yogurt
Give an example of a food system where the protein functional property of solubility is
important - Correct Answers -beverages, protein concentrates
How a protein would be "soluble" in water —> most proteins in globular form.
Hydrophobic aa in core of protein (majority), hydrophilic side chains on srface b/c can
interact w/water
At pH 10, will the protein be soluble? - Correct Answers -no, as increase pH to 10,
globular protein will completely open and unravel and will be fully -ve.
What happens to the charge of aa when we decrease or increase pH? - Correct
Answers -Increase pH -- aa becomes more -ve and increase solubility
Give an example of a food system where the protein functional property of
emulsification is important - Correct Answers -salad dressing, mayonnaise, ice cream,
gravy
Give an example of a food system where the protein functional property of foaming is
important - Correct Answers -meringues, whipped toppings, angel cake, marshmallows
, What alters the properties of food proteins? - Correct Answers -Altered by
environmental conditions (pH, ionic structure, moisture content), processing (heating,
freezing, drying, shearing, pressure) treatments, and interactions with other ingredients.
Protein structure determines functionality.
What causes a protein to be soluble? - Correct Answers -Affected by the balance of
hydrophobic and hydrophilic amino acids on its surface.
Charged amino acids play the most important role in keeping the protein soluble.
At what pH are proteins the least soluble? - Correct Answers -The proteins are least
soluble at their isoelectric point (no net charge).
When do proteins become increasingly soluble? - Correct Answers -The protein
become increasingly soluble as pH is increased or decreased away from the pI.
Decreases pH -- aa becomes +vely charged and increases solubility
Describe "salting in" - Correct Answers -At low salt concentrations protein solubility
increases
Describe salting out - Correct Answers -At high salt concentrations, protein solubility
decreases
How does denaturation help or hinder solubility of proteins? - Correct Answers -Very
high or very low pH denatures the proteins and makes it soluble because lots of
repulsion.
Very high or very low temperature on the other hand will lead to loss in solubility since
exposed hydrophobic groups of the denatured protein lead to aggregation (may be
desirable or undesirable in food products).
Therefore denaturation using pH is more beneficial. Denaturation through heat and
temperature is undesirable in most products
Define a gel - Correct Answers -Gel; a continuous 3D network of proteins that entraps
water.
Types of interactions in a gel - Correct Answers -Protein-proteininteractionandprotein-
water (non-covalent).
A gel can form when proteins are denatured by... - Correct Answers -heat, pH,
pressure, shearing
SYSTEMS EXAM QUESTIONS WITH CORRECT
ANSWERS
5 major functional properties of proteins - Correct Answers -1. Solubility
2. Water-holding ability
3. Gelation
4. Emulsification
5. Foaming
Give an example of a food system where the protein functional property of gelation is
important - Correct Answers -muscle foods, eggs, yogurt, gelatin, tofu, baked goods
Give an example of a food system where the protein functional property of water holding
ability is important - Correct Answers -muscle foods, cheese, yogurt
Give an example of a food system where the protein functional property of solubility is
important - Correct Answers -beverages, protein concentrates
How a protein would be "soluble" in water —> most proteins in globular form.
Hydrophobic aa in core of protein (majority), hydrophilic side chains on srface b/c can
interact w/water
At pH 10, will the protein be soluble? - Correct Answers -no, as increase pH to 10,
globular protein will completely open and unravel and will be fully -ve.
What happens to the charge of aa when we decrease or increase pH? - Correct
Answers -Increase pH -- aa becomes more -ve and increase solubility
Give an example of a food system where the protein functional property of
emulsification is important - Correct Answers -salad dressing, mayonnaise, ice cream,
gravy
Give an example of a food system where the protein functional property of foaming is
important - Correct Answers -meringues, whipped toppings, angel cake, marshmallows
, What alters the properties of food proteins? - Correct Answers -Altered by
environmental conditions (pH, ionic structure, moisture content), processing (heating,
freezing, drying, shearing, pressure) treatments, and interactions with other ingredients.
Protein structure determines functionality.
What causes a protein to be soluble? - Correct Answers -Affected by the balance of
hydrophobic and hydrophilic amino acids on its surface.
Charged amino acids play the most important role in keeping the protein soluble.
At what pH are proteins the least soluble? - Correct Answers -The proteins are least
soluble at their isoelectric point (no net charge).
When do proteins become increasingly soluble? - Correct Answers -The protein
become increasingly soluble as pH is increased or decreased away from the pI.
Decreases pH -- aa becomes +vely charged and increases solubility
Describe "salting in" - Correct Answers -At low salt concentrations protein solubility
increases
Describe salting out - Correct Answers -At high salt concentrations, protein solubility
decreases
How does denaturation help or hinder solubility of proteins? - Correct Answers -Very
high or very low pH denatures the proteins and makes it soluble because lots of
repulsion.
Very high or very low temperature on the other hand will lead to loss in solubility since
exposed hydrophobic groups of the denatured protein lead to aggregation (may be
desirable or undesirable in food products).
Therefore denaturation using pH is more beneficial. Denaturation through heat and
temperature is undesirable in most products
Define a gel - Correct Answers -Gel; a continuous 3D network of proteins that entraps
water.
Types of interactions in a gel - Correct Answers -Protein-proteininteractionandprotein-
water (non-covalent).
A gel can form when proteins are denatured by... - Correct Answers -heat, pH,
pressure, shearing
